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Extending the Bandwidth of an Elliptical Monopole Antenna (.PDF Download)

June 12, 2018
Extending the Bandwidth of an Elliptical Monopole Antenna (.PDF Download)

Wide-bandwidth antennas represent a more compact alternative to the use of multiple antennas to cover the same bandwidth. Numerous design approaches are available for achieving wide antenna bandwidth, including an elliptical monopole antenna developed by the authors. It consists of an elliptical patch fed by coplanar-waveguide (CPW) transmission line and matched to 50 Ω for wideband operation. The antenna was developed through comprehensive parametric studies and the design aid of the three-dimensional (3D) electromagnetic (EM) simulation software CST Microwave Studio from Computer Simulation Technology.

In a radio system, an antenna sends and detects electromagnetic (EM) waves and is considered one of the more important components in a wireless communications system.1 Numerous configurations are available for RF/microwave applications. One option, a planar monopole antenna, is a good candidate for wireless communication services because of its wide impedance bandwidth, omnidirectional radiation pattern, high radiation efficiency, and compact size.2,3

By designing a single antenna that can cover a large bandwidth, it can be used for various applications.4,5 A monopole antenna is one-half of a dipole antenna, almost always mounted above some sort of ground plane. Among the range of broadband monopole configurations that have been developed are circular, square, elliptical, pentagonal, and hexagonal forms (Fig. 1), which can easily be integrated into RF/microwave circuits as well as ultrawideband (UWB) devices.6-8

1. These drawings depict some of the different planar antenna geometries used for broad bandwidths.

When the planar radiating elements of a monopole antenna are etched on a dielectric substrate, a ground plane can be in the form of CPW transmission lines with the radiating elements or in the frame of the dielectric substrate. The radiating elements can be fed by a coaxial cable or microribbon line. Modifying the ground plane in certain ways can increase the antenna bandwidth. CPW enables good impedance matching, omnidirectional radiation patterns, and wide bandwidths at RF, microwave, and millimeter-wave (mmWave) frequencies. These CPW benefits make it a preferable method to feed antennas and to integrate with active devices.9